One application of a surface textured substrate in the solar cell industry is to enhance light absorption. Research shows some wavelengths of incident light reflect from non-textured solar cell surfaces. Texturing causes light to be trapped and results in more efficient solar cells. To make LEDs more efficient, patterned sapphire substrates (PSS) have been developed. Patterned substrates produce brighter LEDs. Using a Sapphire substrate as a base, two layers of GaN (p and n doped) are coated that act as light emitting diode. In unpatterned Sapphire substrates, emitted light reflects back and forth and is trapped between GaN and Sapphire base increasing LED temperature resulting in lower efficiency and less emission of light. PSS helps skip of light and enhances light extraction about 30% more. It also helps for better epitaxial GaN growth.
Currently, the prior art laser material processing systems produce textures or orifices in substrates such as glass or Si by laser exposure techniques such as: ablative machining via direct writing; lithography techniques (coating surface with light sensitive materials and then printing desired pattern then etching). All of the prior art systems have low throughput times and are not cost effective, do not work well with many of the new exotic substrate materials, have problems with the opacity of multiple level substrate stacks, cannot attain the close orifice spacing sought, propagate cracks in the material or leave an unacceptable surface roughness on the orifice sides and surface surrounding the point of initiation as detailed below. In direct laser writing, thermal transport during the laser interaction can lead to large regions of collateral thermal damage (i.e. heat affected zone). While laser ablation processes can be dramatically improved by selecting lasers with wavelengths that are strongly absorbed by the medium (for example, deep UV excimer lasers or far-infrared CO2 laser), the above disadvantages cannot be eliminated due to the aggressive interactions inherent in this physical ablation process. Alternatively, laser ablation can also be improved at the surface of transparent media by reducing the duration of the laser pulse. This is especially advantageous for lasers that are transparent inside the processing medium. When focused onto or inside transparent materials, the high laser intensity induces nonlinear absorption effects to provide a dynamic opacity that can be controlled to accurately deposit appropriate laser energy into a small volume of the material as defined by the focal volume. The short duration of the pulse offers several further advantages over longer duration laser pulses such as eliminating plasma reflections and reducing collateral damage through the small component of thermal diffusion and other heat transport effects during the much shorter time scale of such laser pulses. Femtosecond and picosecond laser ablation therefore offer significant benefits in machining of both opaque and transparent materials. However, machining of transparent materials with pulses even as short as tens to hundreds of femtosecond is also associated with the formation of rough surfaces and microcracks in the vicinity of laser-formed orifices or trench that is especially problematic for brittle materials like Alumnia glasses, doped dielectrics and optical crystals. Further, ablation debris will contaminate the nearby sample and surrounding surfaces. Although laser processing has been successful in overcoming many of the limitations associated with texturing, as mentioned above, new material compositions have rendered the wafers and panels incapable of being laser processed efficiently.
Henceforth, a fast, economical system for texturing and drilling through or stopped orifices in transparent materials emanating from the top or bottom surface, that avoids the drawbacks of existing prior art systems would fulfill a long felt need in the materials processing industry. This new invention utilizes and combines known and new technologies in a unique and novel configuration to overcome the aforementioned problems.